According to the air traffic rules，you should your mobile phone before boarding．
| A．switch over | B．switch on | C．switch off | D．switch round |
He must have had an accident, or he ____ here for class then ．
| A．had to be | B．should be | C．would be | D．would have been |
Put yourself in situations where you will be forced to communicate in English, ____ you will see more progress over time．
| A．or | B．so | C．yet | D．and |
Thousands of people ____ the company stores to leave flowers, notes, even apples with
a bite in the past two weeks．
| A．had been attending | B．had attended |
| C．have been attending | D．attended |
Education is a lifelong process, ____ starting long before the start of schooling．
| A．which | B．that | C．it | D．one |
—Shall we go out for a walk?
—I'm afraid not．We can't go out ___ our work is being done．
| A．before | B．until | C．as | D．after |